Microstructures containing an array of microelements have been disclosed in various patent publications, many of which include openings that allow a fluid exchange between the top and bottom surfaces of the microelement array. The individual microelements typically are designed to penetrate the stratum corneum of animal skin, or to penetrate some other type of membrane. Once the penetration has been accomplished, a fluid (e.g., liquid drugs) can be dispensed into the body from a reservoir in the microstructure, or in the reverse direction, a body fluid can be sampled into such a reservoir in the microstructure.
The proper size and shape of the microelements depends upon many factors, and for some applications (e.g., drug delivery or body fluid sampling through human skin), several different sizes, and especially shapes, will suffice. Some applications of microstructures do not require through-openings; however, for those applications that do need through-openings, it is important to find a way to manufacture such microstructures in an inexpensive (and high-volume) manner, within tolerable accuracy to lower reject rates during the manufacturing of these devices.
Various sizes and shapes of microstructures have been disclosed by the present inventors, in commonly assigned United States patent applications, as noted below. The documents listed below are incorporated herein by reference, in their entirety: INTRACUTANEOUS MICRONEEDLE ARRAY APPARATUS, Ser. No. 09/328,947, filed on Jun. 9, 1999; APPARATUS AND METHOD FOR USING AN INTRACUTANEOUS MICRONEEDLE ARRAY, Ser. No. 09/329,025, filed on Jun. 9, 1999, now U.S. Pat. No. 6,256,533 B1, which issued Jul. 3, 2001; APPARATUS AND METHOD FOR MANUFACTURING AN INTRACUTANEOUS MICRONEEDLE ARRAY, Ser. No. 09/328,946, filed on Jun. 9, 1999, now U.S. Pat. No. 6,312,612 B1, which issued Nov. 6, 2001; INTRACUTANEOUS EDGED MICRONEEDLE APPARATUS, Ser. No. 09/580,780, filed on May 26, 2000; INTRACUTANEOUS MICRONEEDLE ARRAY APPARATUS, Ser. No. 09/580,819, filed on May 26, 2000; METHOD OF MANUFACTURING AN INTRACUTANEOUS MICRONEEDLE ARRAY, Ser. No. 09/579,798, filed on May 26, 2000; METHOD OF MANUFACTURING MICRONEEDLE STRUCTURES USING SOFT LITHOGRAPHY AND PHOTOLITHOGRAPHY, Ser. No. 09/808,534, filed on Mar. 14, 2001; MICROSTRUCTURES FOR TREATING AND CONDITIONING SKIN, Ser. No. 09/952,403, filed on Sep. 14, 2001; MICROSTRUCTURES FOR DELIVERING A COMPOSITION CUTANEOUSLY TO SKIN, Ser. No. 09/952,391, filed on Sep. 14, 2001; MICROSTRUCTURES FOR DELIVERING A COMPOSITION CUTANEOUSLY TO SKIN USING ROTATABLE STRUCTURES, Ser. No. 10/216,148, filed on Aug. 9, 2002.
It would be beneficial to provide an improved method of manufacturing microstructures with openings that extend through the substrate and through the individual microelements, and to do so in a high-volume, low-cost manner. It would also be beneficial to provide a method manufacturing such microstructures in a way that ensures most, or all, of the microelements contains at least one such through-hole within the microelements' perimeter.